Question on a ball dropping( conservation of energy)

AI Thread Summary
A 1 Kg ball is dropped from a height of 7m, resulting in a potential energy of 70J just before impact, which equals its kinetic energy at that moment. The discussion highlights the use of the equations for potential energy (PE = mgh) and kinetic energy (KE = 1/2 mv^2) to calculate energy values. To find the initial rebound velocity and kinetic energy after the bounce, the same potential energy formula can be applied at the new height of 4.5m. The conversation emphasizes the loss of kinetic energy upon impact, which should be accounted for in calculations. Understanding these principles is crucial for solving problems related to the conservation of energy.
Peter-John King
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Homework Statement



A ball of mass 1 Kg is dropped from a height of 7m and rebounds to a height of 4.5m Calculate:
its kinetic energy just before impact
the initial rebound velocity of the ball and kinetic energy. Account for loss of kinetic energy on impact



2. Homework Equations [/B]
i am not sure of all the relevant equations i used pe=mgh and k.e=1/2mv^2

The Attempt at a Solution


I found the answer to a using the formula P.E.=mgh=1x10x7=70J
K.E.=P.E.=70J
I do not know how to find the second answer
 
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Peter-John King said:
I found the answer to a using the formula P.E.=mgh=1x10x7=70J
K.E.=P.E.=70J
Good.

Peter-John King said:
I do not know how to find the second answer
Use the same equation. (A different height, of course.)
 
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